I have a community 29 gallon tank with a sand substrate, but it doesn't look very appealing because of all the fish poop on the sand bed. is there a fish or invertebrate that could clean this mess up (or at least make it look nicer)?

I love my sand substrates for that very reason...all the poop sits on the top. It's a breeze to just vaccuum it all up straight off the top. With gravel or pebbles it falls down in between the cracks. How often are you running a gravel vac (hovering just above the surface of the sand bed)? I do mine once a week and don't really notice the poop becoming an issue until ust a day or two before my water changes.

PS. I just took a look at your tank log and don't see any pics yet. What color sand do you have?

ya gotta be carefull with sand though as there can be "dead spots" that are very toxic to fish and plants. these "dead spots" come from poop left over food and anything else that sits for too long then decomposes and then breaks down and sinks into the bed. as with gravel you can just sink the vac right into it and get all the sludge and crud a little more easy and dead spots dont occur as easy or are cleaned up more easy.

The "dead spots" are called anaerobic pockets and are easily avoided by gently stirring your sand around when doing your weekly water change (filters off during this procedure). Adding Malayan Trumpet (livebearing) snails will aid in tank maintenance. They will constantly turn over the sand, letting oxygen get in, and will also eat up any bits of waste that gets into the sand. Live plants are also great when using a sand substrate. The roots of plants have evolved to live in anaerobic substrates, and carry oyxgen from the water into the substrate. You won't get anaerobic decay in a well-planted aquarium. HTH

i have a white sand substrate. i put a crayfish in there and he started eating all the fish poo!!the tank is pretty clean now (but not perfect). i have kuhli loaches to dig in the sand to prevent anaerobic pockets.

I have a horsehead loach that eats by sifting the sand through his mouth and out his gills at a pretty surprising rate...this helps stir up the bottom a bit to get things up into the filter...at least the small pieces. Of course, he doesn't actually eat the poo.

I vacuum the sand by using a 20oz soda bottle with the bottom cut off. The flow is slow enough that the sand doesn't quite make it's way to the top where it would be sucked out. This way, I can actually stick the bottle down into the sand and get everything out that might have been turned under by the clams or loach.

I saw one of my ghost shrimp chowing down on some when I first put them in...but now they usually just peel fish flakes off of the surface of the water and eat those. I guess they prefer the taste of undigested food. :-\